1. Field of the Invention
The present invention relates generally to a magnesium based amorphous alloy. More specifically, the invention relates to a Mg-based amorphous alloy, which has basically a good glass forming ability, along with an improved ductility.
2. Background of the Related Art
In general, a magnesium alloy is one of lightweight alloys having a high strength-to-weight ratio. The Mg alloy has an excellent vibration, impact, and electromagnetic wave absorbing abilities, a good electrical and heat conductivity, and an enhanced fatigue impact resistance at elevated temperature. Thus, it has a broad range of applications as a lightweighting material, for example, for automotive parts, transportation means, defense industry, and general machinery.
However, mostly crystalline Mg alloys have been used. In order that the Mg-based alloy can be employed for applications necessitating high mechanical properties, a Mg-based amorphous alloy needs to be developed, which is known to have an improved tensile strength, toughness and corrosion-resistance, relative to the conventional crystalline Mg-based alloys.
Thus, up until now, various types of Mg-based amorphous alloys have been proposed as follows.
Examples for a binary Mg-based amorphous alloy include Mg—Ca, Mg—Ni, Mg—Cu, Mg—Zn, Mg—Y, or the like. In addition, a tertiary Mg-based amorphous alloy system is exemplified by Mg—Cu—(Si, Ge, Ln, Y), Mg—Ni—(Si, Ge, Ln), Mg—Zn—(Si, Ge, Ln), Mg—Ca—(Al, Li, Si, Ge, M), Mg—Al-(Ln, Zn) and the like, where Ln is a lanthnide and M is a transition metallic element (Ni, Cu, Zn).
Conventionally, these Mg-based amorphous alloys can be manufactured only in the form of a ribbon having a thickness of several tens of microns or in the powder form, mostly using a rapid solidification method such as a melt spinning method, a splat quenching method, and a liquid atomization method. Thus, there have been lots of limitations in their applications.
Furthermore, recently-developed Mg-based bulk amorphous alloys embrace limitations in their practical use, similarly since they can be manufactured in a bulk form having a diameter of below 4 mm using an injection casting process under vacuum atmosphere. Also, the vacuum atmosphere leads to an increase in the manufacturing cost thereof and a decrease in the production efficiency therefor.
In addition, most of the conventional Mg-based amorphous alloys exhibit a brittle fracture behavior without plastic deformation after the elastic limit thereof, and thus have a limited applicability. In order to overcome these limitations in the conventional Mg-based amorphous alloy, that is, to provide a plastic deformation property at room temperature, extensive research and developments have been carried out. For example, a third element is added to the amorphous matrix, or a heat treatment is applied, to form a composite material so as to have a plastic property, or a post-treatment after forming an amorphous phase is performed to thereby provide a plastic characteristic to the amorphous material.
However, in order to provide a plastic deformation characteristic, research on the basis of thermodynamic and kinetic consideration (boundary condition of amorphous/crystalline) of amorphous-formation has been barely performed. Particularly, even appropriate standards or criteria for general purposes have not been produced yet.